Question

EXPERIMENT 7 Pre-Lab Assignment Determining the Empirical Formula of a Compound Name Date 1. Why is it important to scour the magnesium strip with steel wool at the start of the experiment? 2. Why must the heated crucible be cooled to near room temperature before weighing? 3. Should the Bunsen burner flame be kept heating one area of the crucible? Explain why or why not. 4. If the magnesium ribbon flares up, should you stare at it? Explain.

Answer 1

1) Why is it important to scour the magnesium strip with steel wool at the start of the experiment?
Answer : it is important to scour the magnesium strip with steel wool to remove all the oxide coating which may have been deposited on the ribbon by the reaction of magnesium with atmospheric oxygen.

it is important to remove the oxide coating , to achieve good results.

2) Why must the heated crucible be cooled to near room temperature before weighing?

Answer: The reason you let the dish or crucible cool to room temperature is two-fold. The first reason is safety. You don't want to burn yourself on hot glass or metal. You also don't want to damage your balance with heat either. The other reason is warm objects surrounded by cooler air tend to create small air currents as a result of the hot air rising and colder air moving in to replace it. While these air currents are tiny and cannot be felt by a person, they can affect the mass reading on a balance. So you should wait until the dish is at room temperature so that the reading you get on the balance is steady and accurate.

3)Should the bunsen burner flame be kept heating in one area of the crucible?why or why not.
Answer : No it should not. When a crucible is heated in one spot, it can cause the metal in that particular spot to oxidize and flake off.

4)If the magnesium ribbon flares up, should you stare at it, explain?
Answer : No If the magnesium ribbon flares up, you should not stare at it because a considerable amount of UV light is emitted.

The burning magnesium ribbon produces light of sufficient intensity to cause temporary loss of sight. Avoid looking directly at the light source.